The proposed research is directed toward the systematic identification and isolation of the specific cell surface structures of Streptococcus mutans relevant to its pathogenicity. The approach to be employed involves the production of monoclonal antibodies directed aganist S. mutans surface components and extracellular products utilizing the technique of somatic cell hybridization. Hybridoma antibodies, reactive with single antigenic determinants, are free of contaminating reactivities unlike antisera produced by conventional methods, and may also be obtained in unlimited quantities. The monoclonal antibodies obtained will be tested in vitro for their ability to inhibit adherence of S. mutans to saliva-coated hydroxyapatite, as well as for the ability to inhibit plaque formation by S. mutans in a chemostat model under conditions which approximate those found in the oral cavity. Antibodies with inhibiting activity in one or both assays will be used to isolate mutants lacking the target cell surface or extracellular components involved in these processes. Subsequent isolation and purification of pathologically 'relevant' antigens will be facilitated by linkage of hybridoma antibodies to solid-phase immunoabsorbents, as well as use of hybridoma antibodies to monitor the presence of the molecule under study during isolation procedures. Development of a battery of highly-specific monoclonal antibodies should promote dissection and understanding of the initial attachment and accumulation of S. mutans, in terms of the specific bacterial structures involved. Once isolated and purified, surface components with potential relevance, as expressed by in vitro screening, will be utilized as immunogens in caries protection experiments using the gnotobiotic rat model system.